1. Field of the Invention
This invention relates to a terminal connection structure in which a terminal is press-connected to end portions or intermediate portions of electric wires, and at the same time this connection portion is rendered waterproof. The invention also relates to a method of producing such a structure.
2. Related art
FIG. 4 is a perspective view of a conventional terminal connection structure.
In this structure, exposed conductors 19 of a plurality of electric wires 18 are press-connected together by a pair of pressing pieces 17 and 17 of a joint terminal 16, using a clamp jig (not shown).
Each conductor 19 is beforehand exposed by removing an end portion of a sheath of the wire 18, and as shown in FIG. 5 which is a cross-sectional view taken along the line 5--5 of FIG. 4, the conductors 19 are pressed between and connected to a base plate portion 21 and the pressing pieces 17 of the joint terminal 16.
In the above conventional structure, however, as shown in FIG. 5, spaces 22 are formed between element wires 19a of the conductors 19, between the element wires 19a and the base plate portion 21 and between the element wires 19a and the pressing pieces 17. There has been encountered a problem that water is introduced from the spaces 22 into the wires 18, and moves therealong to intrude into a connected device (not shown) to cause electrocorrosion (corrosion). Another problem is that because of the provision of the spaces 22, an electrical contact resistance between the element wire 19a, as well as an electrical contact resistance between the element wires 19a and the terminal 16, increases. A further drawback is that where the conductor 19 is narrow, the element wire 19a is liable to rupture by a tension or the like.
For another example, a waterproof connector shown in FIG. 11 has been generally known as a waterproof connector using a holding and clamping terminal. In this waterproof connector, a terminal 130 is received in a terminal receiving portion 125 of a connector housing 124. An insulated wire 121 is inserted into a waterproof rubber plug 126 so as to tightly contact therewith, and the waterproof rubber plug 126 is fitted into the terminal receiving portion 125 so as to tightly contact therewith to block the terminal receiving portion 125.
On the other hand, the terminal 130 is formed by the working of punching a conductive metal plate. The terminal 130 has an insulation barrel 130a for holding and clamping a small-diameter cylindrical portion 128 of the waterproof rubber plug 126 so as to hold the cylindrical portion 128 together with the insulated wire inserted into the cylindrical portion 128, and a wire barrel 130c for holding and clamping conductors 123 exposed by separating an insulating coating 121.
Thus, in the waterproof connector having such a conventional structure, the waterproof rubber plug 126 cuts off water which would enter the terminal receiving portion along the outer wall surface of the housing. At the same time, the insulation barrel 130a urges the rubber plug 126 against the outer surface of the wire, so that the terminal can prevent water which would enter the terminal receiving portion through a wire insertion portion of the rubber plug 126. In such a manner, the waterproof connector is made superior in watertight structure.
In the above-mentioned waterproof connector, however, for example, in such a case where the connector-connected wire 121 is further branched and connected through a joint terminal 131 as shown in FIG. 11, there has been a case where water (shown by the arrow in the drawing) intrudes into a wire coating through a wire-terminal portion connected to the joint terminal 131, passes a wire connection portion which has been press fitted by the insulation barrel 130a, and flows into the terminal receiving portion 125 between the conductors 123. Accordingly, there has been a fear that a leak current is generated between adjacent terminals.
As means to solve the foregoing problem, it can be considered that a terminal has such a shape that an insulating coating portion and conductors of a wire end portion can be held and cramped integrally and continuously so that water intruding between the conductors cannot leak out of the terminal. However, in such a structure where the insulating coating and the conductors are held and cramped integrally, there has been a problem that the property of electric contact in a conductor held and cramped portion is deteriorated by the difference in holding and clamping diameter so as to decrease reliability.
Means to prevent water from flowing out of a terminal is disclosed in Japanese Patent Unexamined Publication No. Sho-60-119086. In this means, a cap is provided to cover a wire connection portion of a terminal, and a sealing material is charged into the cap. In this means, it is indeed possible to obtain a waterproof effect at a wire end portion including a terminal, but it has not been considered to make the water proof effective to the whole of the connector including its housing.